#define _CRT_SECURE_NO_WARNINGS  1
#include<stdio.h>
int main()
{
	double i = 0;
	double sum = 0;
	double flag = 1;
	for (i = 1; i < 101; i++)
	{
		sum = sum + 1.0*flag / i;
		flag = -flag;
	}
	printf("%lf", sum);
	return 0;
}